Electromagnetic translating system



May 28, 1935. B. F. MIESSNER ELECTROMAGNETIC TRANSLATING SYSTEM FiledJune 17, 1932 2 Sheets-Sheet l May 28, 1935. B. F. MIESSNER 2,002,919

ELECTROMAGNETIC TRANSLATING SYSTEM Filed Ju ne 17, 1952 2 Sheets-Sheet 2INVENTOR:- amen/n z mas/15k;

Patented May 28, 1935 UNITED STATES PATENT OFFICE ELECTROMAGNETIC TRANSLATIN G SYSTEM Application June 17, 1932, Serial No. 617,738

7 Claims.

This invention relates to electromagnetic translating systems and moreparticularly to those systems employing translating devices including afield coil energizable to provide an intense magnetic field, and adynamic coilpositioned in such field and connected to a source orreceiver of electric oscillations.

An object of the invention is the provision of a system of one or moreof such translating devices whose field coil or coils may be suppliedwith pulsating direct current, or incompletely filtered rectifiedcurrents, without disturbing effect on the dynamic coil or coils. Afurther object of the invention is the provision of a system comprisinga plurality of such devices so positioned, and having field and dynamiccoils respectively so interconnected, as to effect eflicient translationwithout producing undesirable hum in their combined acoustic or electricoutput as a result of pulsations or ripples which may be present in thefield energizing current. Other and allied objects will more fullyappear from the following description and the appended claims.

While I contemplate no limitation of my invention to sound reproducers,or devices for electroacoustic translation, these have been selected asrepresentative translating devices of the class described with which toillustrate my invention. Thus in the detailed description of myinvention hereinafter set forth, reference is had to the accompanyingdrawings, of which:-

Figure 1 is a cross-sectional view of one embodiment of my inventionemploying two suitably arranged sound reproducers;

Figure 2 is a schematic diagram illustrating suitable interconnectionsof the field and dynamic coils, respectively, of the reproducers ofFigure l; and

Figure 3 is a cross-sectional view of an alternative embodiment of myinvention in which a modified form of reproducer is substituted for oneof the reproducers of Figure 1.

In Figure l I have shown two identical reproducers, each separate one ofwhich may be of conventional design. Thus each may comprise for examplea cylindrical element or casing I of magnetic material having anintegral closure at one end and carrying at the other end removable disc4, also of magnetic material. While no mounting for casing I is shown,it will be. understood that it may be supported in a stationary positionin any suitable manner. To the center of the integral end of thecylindrical element l is tightly afiixed central core 2; also ofmagnetic material, core 2 protruding through a hole in disc 4 andforming therewith a slight annular gap 3. Positioned in the gap 3 may bethe dynamic coil 6, wound for example about cylindrical coil form 8, towhich may be afiixed the diaphragm "I. To the coil form may be attachedfiexible disc 21; and this may be centrally mounted, as by bolt 29 andspacer 28, to the end of core 2. This manner of support of the dynamiccoil 6 is illustrative only, it being understood that other well-knownsupporting means are available meeting the requirement of permittingrelatively unimpeded vibration of the dynamic coil 6 in the direction ofthe axis of the core 2 while retaining the coil 6 and its support 8 freeof contact with core 2 or disc to each of which they are preferably veryclosely spaced.

Considering the action of a single reproducer such as either of thoseshown in Figure 2, it will be understood that energization of the fieldcoil with pure unidirectional current will produce a strong magneticfield in the central core 2, in the casing I, and across the gap 3,there cutting the dynamic coil 6. The interaction with this steady fieldof the field produced by a current pulse traversing the dynamic coilwill produce a motion of the dynamic coil either toward or away from thefield coil 5, according to the polarization of the central core 2 and tothe direction of the current fiow in the dynamic coil. Thus the seriesof pulses which make up sound representing currents which may besupplied to the dynamic coil produce a corresponding series of motionsof the dynamic coil and diaphragm, thus operating the reproducer. Itwill further be understood that if the field energizing currentcontains, in addition to pure unidirectional current, a pulsating orripple component, corresponding voltage pulsations will be induced intothe dynamic coil, and corresponding current pulsations will flowtherein. The dynamic coil will thereupon execute a vibratory motion inaccordance therewith, over and above such motion as it may properly andintendedly execute.

In order to reduce or eliminate this undesired vibratory motion it hasbeen common practice to employ, in series with the dynamic coil of areproducer of this type, a stationary bucking coil, so positioned thatthere will be induced therein pulsations or ripple voltages ofapproximately the same amplitude as those induced in r obstacles toperfection of result must always be.

coped with in the use of such a system. These are, first, the waste inthe bucking coil of sound representing input power, and secondly, thediificulty of obtaining perfectly similar amplitudes, phases and waveforms of the pulsations respectively induced in the two coils. While Ihave shown, for example in United States patents to me Numbers 1,859,454and 1,8593522; highly efiective means of coping with these problems, thepresent invention is directed to their complete circumvention. Thus lshow-m each ofthe embodiments of this invention two dynamic coils intowhich the pulsations induced by field excitation may be entirelysimilar. Thesecoils are interconnected for mutual opposition or can"-cellation of these pulsations. Both coils'are fully effective, however,in operating.theudiaphragm or diaphragms of the system.

In Figure 2 I illustrate typical interconnections of the fieldanddynamic coils; respectiveiy', of the. two reproducers showniini Figure.l. The field coils 5 may be connected together either in parallel asshown, or in series,.- and to: their energizing source 26 ofv pulsatingdirect current. The dynamic coils 5 mayalso be connected together inseries, and to the'secon'dary cfan. input transformer 23, the primary ofwhich may be supplied with sound representing currents. The relative.polingof the two dynamic coils will depend on the relation in which thefield coils have been poled, the criterion being simply that thepulsations induced in each dynamic coil by the associated fieldexcitation mutually cancel in their common circuit. Thus in'Figu'res land 2 the coil terminals of the lower reproducerhave been numberedterminals to the other, the dynamic. coils should be connected to effectoppositionof voltages at differently numbered; terminals of the tworespectively. V

In the case of two similar?reproducersfinterr connections of field anddynamic coils asv described above will" be found to cause phaseopposition of the vibratory motions, respectively executed by the twodynamic coils in accordance with sound. representing currents fromtransformer 23, and hence phase opposition ofthe sound outputs of the.reproducers.

ducer' relative to that of the other has been reversed simultaneouslywiththe desired phase reversal of pulsations induced inone dynamic coilrelative to thatof the pulsations induced in the other. The phase ofsound output of one reproducer must therefore be re-reversed rela--,tive tothat of the other. In Figure l I show one method of effectingsuch re-reversal.. This is an acoustic method+the use of the back-sideradiation of the diaphragm of the other. Thus the two reproducers may beoppositely directed against oppositesides of baflle; 9, holes H- thereinbeing provided of approximately the respective outside diameters ofthediaphragms 7-. Limp annular rings ill have been illustrated securedto In' other words, the phase of output sound of one. reproztheperipheries of the diaphragms and to the baffle 9 around such holes tocomplete the bafiiing action; but it will be understood that eachreproucers may be provided with a diaphragmframe and this in turnsecured to the baflie if desired.

In Figure 3 I show an embodiment of my invention wherein I againelectrically reverse the phases of the induced pulsations and soundoutput in and from one reproducer, and mechanically, rather thanacoustically, reverse the phase of soundioutput from one reproducer tocoincide with that of the other. In this figure the upper-shownreproducer may be entirely similar to either of therreproducers ofFigure 1. The lower shown; reproducer is, modified, however, in thefollowing respectsf- Thefiexible disc 2?. supporting the dynamic coil inFigure 1 may be omitted, and its function otherwise performed, as bythree or more flexible flanges 32 extending outwardly from-the coil form8.andxeach:supportedsat its extremities-,as was the flexible disc at-itscenter, by azspacer 28.-

and bolt 29-. A rigid disc- 3! may be providedin the position formerlyoccupied by 21,.and tothe center of this disc be .afiixed rodisl freelypassing. through axial hole 35 in central core 2; At the: other endofthe reproducer. this rod be attached to a similar rigid disc 33,whichmay; bez

flexibly supported in manner similar to:.the support of. disc3fiandcoilz li -ire, by fiexible flanges, spacers and bolts designatedas 32', 28' and 29'. In this embodiment the electrical:interconnections. ofthe coils of: the two reproducers may be entirelysimilar to those shown in Figure2 for 5 the preceding embodiment of myinvention. The phase of the sound output of the lower repro-- ducerhaving been mechanically reversed, how ever, the front-side radiation ofbothadiaphragms maybe employed. I

In both. the embodiments ofmy invention as thus far described, Ihaveshown a series interconnection of the dynamic coils; whereby pulsa-ations therein induced from the field excitation are mutuallyelectrically cancelled. Iimayhow'ever, alternatively employ a; parallelconnection, opposing in that terminals. of the two respective dynamiccoils of opposite instantaneous polarity areqconnect-ed together. .Inthis case the pulsations. will not be electrically. cancelled, each.dia-. phragm vibrating. in accordance. therewith. These undesiredvibrations. of the diaphragms of the two reproducers will form part ofthe'soundoutput from each, but will be respectively in: phase with each:other at the same time thatthe intended sound outputs are of opposite.phase. But upon the above described reversal. of phase of total soundoutput from one reproducer relative to that of the other to obtain"phase. coincience of the desired sound output, the: undesired vibrationsof the two" diaphragms" become respecand that the scope of my inventionis not to be determined by the particularly illustrated embodiments, butrather by the appended claims.

I claim:-

1. In an electromagnetic translating system, the combination of twosound reproducers each including a magnetic circuit wherein is providedan air-gap and including a dynamic coil operatively located in saidair-gap and a diaphragm coupled tosaid coil; a common source ofpulsating direct current for exciting said magnetic cirouits; a commonsource of sound representing oscillations for energizing said dynamiccoils; electrical interconnections between said two reproducers wherebythe pulsations respectively induced in said dynamic coils by saidexcitation mutually cancel; and a common baille for the diaphragms ofsaid reproducers, said diaphragms being so disposed with respect to saidbaflie that their radiations on either one side of said baflle combinein aiding phase.

2. In an electromagnetic translating system, the combination of twosubstantially similar translating devices each including a magneticcircuit wherein is provided an air-gap and including a dynamic coiloperatively located in said air-gap, a diaphragm, and means couplingsaid diaphragm to said coil; a common source of pulsating direct currentfor exciting said magnetic circuits; an electrical work circuitconnected with both said dynamic coils; electrical interconnectionsbetween said two translating devices whereby the pulsations respectivelyinduced in said dynamic coils by said excitation mutually cancel; and acommon baffle for the diaphragms of said two translating devices, saidtranslating devices being disposed on respectively opposite sides ofsaid baflle.

3. In an electromagnetic translating system, the combination of twotranslating devices each including a magnetic circuit wherein isprovided an air-gap and including a dynamic coil operatively located insaid air-gap, a diaphragm, and means coupling said diaphragm to saiddynamic coil, said coupling means in one only of said translatingdevices including means for reversing the phase of vibration of thediaphragm relative to the dynamic coil of such translating device; acommon source of pulsating direct current for exciting said magneticcircuits; an electrical work-circuit connected with both said dynamiccoils; electrical interconnections between said two translating deviceswhereby the pulsations respectively induced in said dynamic coilsmutually cancel; and a common bafile for the diaphragms of said twotranslating devices, said translating devices being disposed on the sameside of said baflle.

4. The method of operating two substantially similar electromagneticreproducers each including a magnetic circuit wherein is provided anairgap and including a dynamic coil operatively located in said air-gapand a diaphragm coupled to said coil, which comprises exciting saidmagnetic circuits with similar pulsating direct current to polarizesimilarly respectively corresponding sides of said two gaps, supplyingsound-representing currents from a common source to said dynamic coilsin respectively opposite phase, and combining the sound radiations fromrespectively opposite sides of said two diaphragms.

5. The method of operating two substantially similar electromagneticsound reproducers each including a magnetic circuit wherein is providedan air-gap and including a dynamic coil operatively located in saidair-gap and a diaphragm coupled to said coil, which comprises excitingsaid magnetic circuits with similar pulsating direct current to polarizeoppositely respectively corresponding sides of said two gaps, supplyingsound-representing currents from a common source to said dynamic coilsin respectively similar phase, and combining the sound radiations fromrespectively opposite sides of said two diaphragms.

6. The method of operating two electromagnetic sound reproducers eachincluding a magnetic circuit wherein is provided an air-gap andincluding a dynamic coil operatively located in said air-gap and adiaphragm vibrated by said coil, which comprises exciting said magneticcircuits with similar pulsating direct current to polarize similarlyrespectively corresponding sides of said two gaps, supplying soundrepresenting currents from a common source to said dynamic coils inrespectively opposite phase, reversing the phase of Vibration of oneonly of said diaphragms with respect to its associated dynamic coil, andcombining the radiations from respectively corresponding sides of saidtwo diaphragms.

7. The method of operating two electromagnetic sound reproducers eachincluding a magnetic circuit wherein is provided an air-gap andincluding a dynamic coil operatively located in said air-gap and adiaphragm vibrated by said coil, which comprises exciting said magneticcircuits with similar pulsating direct current to polarize oppositelyrespectively corresponding sides of said two gaps, supplying soundrepresenting currents from a common source to said dynamic coils inrespectively similar phase, reversing the phase of vibration of one onlyof said diaphragms with respect to its associated dynamic coil, andcombining the radiations from respectively corresponding sides of saidtwo diaphragms.

BENJAMIN F. MIESSNER.

